The present invention relates to a polarized electroluminescence element and a method for fabricating the polarized electroluminescence element, and more particularly to a polarized electroluminescence element used in a backlight source of a display.
An electroluminescence element emits light when a high electric field is applied thereon, and can be used for a product having a light-emitting flat panel display.
For certain applications particularly in the field of display elements, emission of polarized light is particularly important. The backlight source of conventional liquid crystal displays, e.g. video display units for computers, has to be polarized. Generally, the light-emitting material of the electroluminescence element should be in regular alignment to emit polarized electroluminescence.
A well-known polymer, for example poly(p-phenylene vinylene) (PPV) has already been used in electroluminescence elements. PPV is arranged ordinarily in a direction of orientation by rubbing unidirectionally. However, the alignment of the PPV material is not fully unidirectional. Therefore, the emission efficiency of the electroluminescence element composed of PPV is not high. In addition, there are some drawbacks of the unidirectional rub. One is that the surface of the film is easily destroyed, and the other is that the pollution of the crusher may be formed.
For improving the emission efficiency of the electroluminescence, an electron-hole transporting layer may be added to the light-emitting layer. A known electron-hole transporting layer is made of AlQ3 which is a complex of aluminum with 8-hydroxy quinoline. In addition, the electron-hole transporting layer can also be made of discotic liquid crystal molecules. However, the mission efficiency of the electroluminescence is not improved because the electron-hole transporting layer is not in regular alignment.
Hence, for improving the emission efficiency, the present invention discloses an electroluminescence element and a method for fabricating the electroluminescence element so as to overcome the problems described above.
It is therefore an object of the present invention to provide a polarized electroluminescence element for a display.
In accordance with the present invention the polarized electroluminescence element includes a substrate, an orientation-inducing layer situated on the substrate and in a first direction of orientation, and a light-emitting layer situated on the orientation-inducing layer and made of a mixture of an electroluminescent material and an oriented material for emitting polarized electroluminescence, wherein the electroluminescent material and the oriented material are in a second direction of orientation corresponding to the first direction of orientation.
Preferably, the substrate is a glass plate.
Preferably, the orientation-inducing layer is a conductive layer.
Preferably, the orientation-inducing layer is made of polyimide.
In accordance with the present invention, the second direction of orientation is parallel to the first direction of orientation of the orientation-inducing layer. In addition, the oriented material of the light-emitting layer is guided by the orientation-inducing layer to display in the second direction of orientation and performs electron-hole transport in a direction perpendicular to the light-emitting layer.
Preferably, the oriented material of the light-emitting layer is discotic liquid crystal molecules. The electroluminescent material of the light-emitting layer is guided by the oriented material to display in the second direction of orientation.
Preferably, the electroluminescent material of the light-emitting layer is one of polyimide and polyphenylamide.
Furthermore, the light-emitting layer has a structure of cross-linking polymer.
Certainly, the display could be an electroluminescence display.
Certainly, the display could be a liquid crystal display.
It is another object of the present invention to provide a polarized electroluminescence element used in a backlight source of a display
In accordance with the present invention, the polarized electroluminescence element includes a substrate, and a light-emitting layer situated on the substrate and made of a mixture of an electroluminescent material and discotic liquid crystal molecules in a direction of orientation for emitting polarized electroluminescence and performing electron-hole transport in a direction perpendicular to the light-emitting layer.
It is another object of the present invention to provide a method for fabricating a polarized electroluminescence element.
In accordance with the present invention, the method includes steps of a) providing a substrate, b) forming an orientation-inducing layer on the substrate, c) performing an orientation-inducing process on the orientation-inducing layer to make the orientation-inducing layer align in a first direction of orientation, d) providing a mixture of an electroluminescent material and an oriented material, e) forming the mixture on the orientation-inducing layer to be a light-emitting layer, and f) inducing the oriented material of the light-emitting layer by the orientation-inducing layer to align in a second direction of orientation corresponding to the first direction of orientation and inducing the electroluminescent material of the light-emitting layer to align in the second direction of orientation.
In addition, the orientation-inducing layer formed on the substrate is performed by coating. Certainly, the orientation-inducing process could be performed by exposure to light, or the orientation-inducing process could be performed by rubbing.
Preferably, the mixture is formed on the orientation-inducing layer by coating.
Preferably, the orientation-inducing process is performed at the temperature ranged from 80xc2x0 C. to 120xc2x0 C.
In accordance with the present invention, each the electroluminescent material and the oriented material further includes photo-polymerization functional groups.
In accordance with the present invention, the method further includes a step of cross-linking the electroluminescent material and the oriented material by exposure to light.
In addition, the second direction of orientation is parallel to the first direction of orientation.
It is another object of the present invention to provide a method for improving emission efficacy of a light-emitting layer in a polarized electroluminescence element.
In accordance with the present invention, the method includes steps of a) forming a light-emitting layer by mixing an electroluminescent material and an electron-hole transporting material, and b) inducing the electron-hole transporting material by an orientation-inducing layer to align in a direction of orientation, and inducing the electroluminescent material to align in the direction of orientation.
Preferably, the electron-hole transporting material is discotic liquid crystal molecules.
The present invention may best be understood through the following descriptions with reference to the accompanying drawings, in which: